libertas: add abilty to set DMA buffers alignmnet for SPI interface in compile time

PATCH In review Mike Rapoport 3 participants 5 messages Feb 3, 2009 – Feb 4, 2009 Networking drivers (wireless)

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Mike Rapoport

author

2009-02-03 07:34 UTC #0 lore raw

PATCH 1/1 libertas: add abilty to set DMA buffers alignmnet for SPI interface in compile time

Different SPI controllers pose different alignment requirements on DMAable buffers. It's possible to alter the SPI controller driver to use it's own properly aligned buffers for DMA and copy the data it gets from the client into these buffers. However, this approach also impacts overall performance. Adding ability to set DMA buffers alignment for SPI interface in compile time prevents unnecessary memcpy calls.

Signed-off-by Mike Rapoport <[email protected]>

---
 drivers/net/wireless/Kconfig           |   10 ++++++++++
 drivers/net/wireless/libertas/if_spi.c |   27 ++++++++++++++++-----------
 2 files changed, 26 insertions(+), 11 deletions(-)

drivers/net/wireless/Kconfig +10 -0

index fe819a7..3bbb7b2 100644
@@ -157,6 +157,16 @@ config LIBERTAS_SPI
 	---help---
 	  A driver for Marvell Libertas 8686 SPI devices.
 
+config LIBERTAS_SPI_DMA_ALIGN
+	int "DMA buffers alignment for SPI interface"
+	depends on LIBERTAS_SPI
+	default 4 if !ARCH_PXA
+	default 8 if ARCH_PXA
+	---help---
+	  Different SPI controllers pose different alignment
+	  requirements on DMAable buffers. Allow proper setting of
+	  this value in compile-time.
+
 config LIBERTAS_DEBUG
 	bool "Enable full debugging output in the Libertas module."
 	depends on LIBERTAS

drivers/net/wireless/libertas/if_spi.c +16 ~~-11~~

index 07311e7..3499948 100644
@@ -33,10 +33,12 @@
 #include "dev.h"
 #include "if_spi.h"
 
+#define DMA_ALIGN CONFIG_LIBERTAS_SPI_DMA_ALIGN
+
 struct if_spi_packet {
-	struct list_head		list;
-	u16				blen;
-	u8				buffer[0] __attribute__((aligned(4)));
+	struct list_head	list;
+	u16			blen;
+	u8			buffer[0] __attribute__((aligned(DMA_ALIGN)));
 };
 
 struct if_spi_card {

@@ -73,7 +75,7 @@ struct if_spi_card {
 	struct semaphore		spi_ready;
 	struct semaphore		spi_thread_terminated;
 
-	u8				cmd_buffer[IF_SPI_CMD_BUF_SIZE];
+	u8				cmd_buffer[IF_SPI_CMD_BUF_SIZE] __attribute__((aligned(DMA_ALIGN)));
 
 	/* A buffer of incoming packets from libertas core.
 	 * Since we can't sleep in hw_host_to_card, we have to buffer

@@ -665,10 +667,13 @@ static int if_spi_c2h_cmd(struct if_spi_card *card)
 	BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE < LBS_CMD_BUFFER_SIZE);
 	BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE < LBS_UPLD_SIZE);
 
-	/* It's just annoying if the buffer size isn't a multiple of 4, because
-	 * then we might have len <  IF_SPI_CMD_BUF_SIZE but
-	 * ALIGN(len, 4) > IF_SPI_CMD_BUF_SIZE */
-	BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE % 4 != 0);
+	/*
+	 * It's just annoying if the buffer size isn't a multiple of
+	 * DMA_ALIGN, because then we might have
+	 * len < IF_SPI_CMD_BUF_SIZE but
+	 * ALIGN(len, DMA_ALIGN) > IF_SPI_CMD_BUF_SIZE
+	 */
+	BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE % DMA_ALIGN != 0);
 
 	lbs_deb_enter(LBS_DEB_SPI);

@@ -691,7 +696,7 @@ static int if_spi_c2h_cmd(struct if_spi_card *card)
 
 	/* Read the data from the WLAN module into our command buffer */
 	err = spu_read(card, IF_SPI_CMD_RDWRPORT_REG,
-				card->cmd_buffer, ALIGN(len, 4));
+				card->cmd_buffer, ALIGN(len, DMA_ALIGN));
 	if (err)
 		goto out;

@@ -747,7 +752,7 @@ static int if_spi_c2h_data(struct if_spi_card *card)
 	data = skb_put(skb, len);
 
 	/* Read the data from the WLAN module into our skb... */
-	err = spu_read(card, IF_SPI_DATA_RDWRPORT_REG, data, ALIGN(len, 4));
+	err = spu_read(card, IF_SPI_DATA_RDWRPORT_REG, data, ALIGN(len, DMA_ALIGN));
 	if (err)
 		goto free_skb;

@@ -940,7 +945,7 @@ static int if_spi_host_to_card(struct lbs_private *priv,
 		err = -EINVAL;
 		goto out;
 	}
-	blen = ALIGN(nb, 4);
+	blen = ALIGN(nb, DMA_ALIGN);
 	packet = kzalloc(sizeof(struct if_spi_packet) + blen, GFP_ATOMIC);
 	if (!packet) {
 		err = -ENOMEM;

Signature · 6 lines

1.5.6.4


-- 
Sincerely yours,
Mike.

Dan Williams

2009-02-03 15:48 UTC #1 lore raw

Quoted 6 lines · Mike Rapoport

Different SPI controllers pose different alignment requirements on DMAable buffers. It's possible to alter the SPI controller driver to use it's own properly aligned buffers for DMA and copy the data it gets from the client into these buffers. However, this approach also impacts overall performance. Adding ability to set DMA buffers alignment for SPI interface in compile time prevents unnecessary memcpy calls.

I'd still rather that alignment constraints were handled in the *controller* code, where the constraint actually is. If this path is followed, then every SPI-connected device for a platform would have to have specific hacks for every platform, which is quite unmaintainable. Is there a good way to fit the alignment constraints into the SPI controller code?

Dan

Quoted 113 lines

Signed-off-by Mike Rapoport <[email protected]>

---
 drivers/net/wireless/Kconfig           |   10 ++++++++++
 drivers/net/wireless/libertas/if_spi.c |   27 ++++++++++++++++-----------
 2 files changed, 26 insertions(+), 11 deletions(-)

drivers/net/wireless/Kconfig +10 -0

index fe819a7..3bbb7b2 100644
@@ -157,6 +157,16 @@ config LIBERTAS_SPI
 	---help---
 	  A driver for Marvell Libertas 8686 SPI devices.
 
+config LIBERTAS_SPI_DMA_ALIGN
+	int "DMA buffers alignment for SPI interface"
+	depends on LIBERTAS_SPI
+	default 4 if !ARCH_PXA
+	default 8 if ARCH_PXA
+	---help---
+	  Different SPI controllers pose different alignment
+	  requirements on DMAable buffers. Allow proper setting of
+	  this value in compile-time.
+
 config LIBERTAS_DEBUG
 	bool "Enable full debugging output in the Libertas module."
 	depends on LIBERTAS

drivers/net/wireless/libertas/if_spi.c +16 ~~-11~~

index 07311e7..3499948 100644
@@ -33,10 +33,12 @@
 #include "dev.h"
 #include "if_spi.h"
 
+#define DMA_ALIGN CONFIG_LIBERTAS_SPI_DMA_ALIGN
+
 struct if_spi_packet {
-	struct list_head		list;
-	u16				blen;
-	u8				buffer[0] __attribute__((aligned(4)));
+	struct list_head	list;
+	u16			blen;
+	u8			buffer[0] __attribute__((aligned(DMA_ALIGN)));
 };
 
 struct if_spi_card {

@@ -73,7 +75,7 @@ struct if_spi_card {
 	struct semaphore		spi_ready;
 	struct semaphore		spi_thread_terminated;
 
-	u8				cmd_buffer[IF_SPI_CMD_BUF_SIZE];
+	u8				cmd_buffer[IF_SPI_CMD_BUF_SIZE] __attribute__((aligned(DMA_ALIGN)));
 
 	/* A buffer of incoming packets from libertas core.
 	 * Since we can't sleep in hw_host_to_card, we have to buffer

@@ -665,10 +667,13 @@ static int if_spi_c2h_cmd(struct if_spi_card *card)
 	BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE < LBS_CMD_BUFFER_SIZE);
 	BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE < LBS_UPLD_SIZE);
 
-	/* It's just annoying if the buffer size isn't a multiple of 4, because
-	 * then we might have len <  IF_SPI_CMD_BUF_SIZE but
-	 * ALIGN(len, 4) > IF_SPI_CMD_BUF_SIZE */
-	BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE % 4 != 0);
+	/*
+	 * It's just annoying if the buffer size isn't a multiple of
+	 * DMA_ALIGN, because then we might have
+	 * len < IF_SPI_CMD_BUF_SIZE but
+	 * ALIGN(len, DMA_ALIGN) > IF_SPI_CMD_BUF_SIZE
+	 */
+	BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE % DMA_ALIGN != 0);
 
 	lbs_deb_enter(LBS_DEB_SPI);

@@ -691,7 +696,7 @@ static int if_spi_c2h_cmd(struct if_spi_card *card)
 
 	/* Read the data from the WLAN module into our command buffer */
 	err = spu_read(card, IF_SPI_CMD_RDWRPORT_REG,
-				card->cmd_buffer, ALIGN(len, 4));
+				card->cmd_buffer, ALIGN(len, DMA_ALIGN));
 	if (err)
 		goto out;

@@ -747,7 +752,7 @@ static int if_spi_c2h_data(struct if_spi_card *card)
 	data = skb_put(skb, len);
 
 	/* Read the data from the WLAN module into our skb... */
-	err = spu_read(card, IF_SPI_DATA_RDWRPORT_REG, data, ALIGN(len, 4));
+	err = spu_read(card, IF_SPI_DATA_RDWRPORT_REG, data, ALIGN(len, DMA_ALIGN));
 	if (err)
 		goto free_skb;

@@ -940,7 +945,7 @@ static int if_spi_host_to_card(struct lbs_private *priv,
 		err = -EINVAL;
 		goto out;
 	}
-	blen = ALIGN(nb, 4);
+	blen = ALIGN(nb, DMA_ALIGN);
 	packet = kzalloc(sizeof(struct if_spi_packet) + blen, GFP_ATOMIC);
 	if (!packet) {
 		err = -ENOMEM;

Signature · 11 lines

1.5.6.4


-- 
Sincerely yours,
Mike.

--
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Andrey Yurovsky

2009-02-03 16:17 UTC #2 lore raw

Quoted 8 lines · Dan Williams

Quoted 6 lines · Mike Rapoport
Different SPI controllers pose different alignment requirements on DMAable buffers. It's possible to alter the SPI controller driver to use it's own properly aligned buffers for DMA and copy the data it gets from the client into these buffers. However, this approach also impacts overall performance. Adding ability to set DMA buffers alignment for SPI interface in compile time prevents unnecessary memcpy calls.

Quoted 8 lines

I'd still rather that alignment constraints were handled in the *controller* code, where the constraint actually is. If this path is followed, then every SPI-connected device for a platform would have to have specific hacks for every platform, which is quite unmaintainable. Is there a good way to fit the alignment constraints into the SPI controller code?
Dan

"struct spi_device" currently stores things like the IRQ number (ie:
"spi->irq"), how about we add an optional field to struct spi_device, something like "dma_alignment" that drivers can use as a hint? On PXA it would be set to 8, on Blackfin it can be left at 0 or set to 4 or something.

In our case we have:
- a device that needs ALIGN(4) or a multiple of 4 to work
- a controller that wants ALIGN(8)

So our if_spi_probe would then use the spi->dma_alignment field to choose a sane value to use with ALIGN. This would work for run-time stuff but it wouldn't help us align a static buffer correctly while Mike's approach would, though we could do something fancy to align that too. What do you think? Thanks,

-Andrey

Quoted 119 lines

Quoted 105 lines

Signed-off-by Mike Rapoport <[email protected]>

---
 drivers/net/wireless/Kconfig           |   10 ++++++++++
 drivers/net/wireless/libertas/if_spi.c |   27 ++++++++++++++++-----------
 2 files changed, 26 insertions(+), 11 deletions(-)

drivers/net/wireless/Kconfig +10 -0

index fe819a7..3bbb7b2 100644
@@ -157,6 +157,16 @@ config LIBERTAS_SPI
      ---help---
        A driver for Marvell Libertas 8686 SPI devices.
 
+config LIBERTAS_SPI_DMA_ALIGN
+     int "DMA buffers alignment for SPI interface"
+     depends on LIBERTAS_SPI
+     default 4 if !ARCH_PXA
+     default 8 if ARCH_PXA
+     ---help---
+       Different SPI controllers pose different alignment
+       requirements on DMAable buffers. Allow proper setting of
+       this value in compile-time.
+
 config LIBERTAS_DEBUG
      bool "Enable full debugging output in the Libertas module."
      depends on LIBERTAS

drivers/net/wireless/libertas/if_spi.c +16 ~~-12~~

index 07311e7..3499948 100644
@@ -33,10 +33,12 @@
 #include "dev.h"
 #include "if_spi.h"
 
+#define DMA_ALIGN CONFIG_LIBERTAS_SPI_DMA_ALIGN
+
 struct if_spi_packet {
-     struct list_head                list;
-     u16                             blen;
-     u8                              buffer[0] __attribute__((aligned(4)));
+     struct list_head        list;
+     u16                     blen;
+     u8                      buffer[0] __attribute__((aligned(DMA_ALIGN)));
 };
 
 struct if_spi_card {

@@ -73,7 +75,7 @@ struct if_spi_card {
      struct semaphore                spi_ready;
      struct semaphore                spi_thread_terminated;
 
-     u8                              cmd_buffer[IF_SPI_CMD_BUF_SIZE];
+     u8                              cmd_buffer[IF_SPI_CMD_BUF_SIZE] __attribute__((aligned(DMA_ALIGN)));
 
      /* A buffer of incoming packets from libertas core.
       * Since we can't sleep in hw_host_to_card, we have to buffer

@@ -665,10 +667,13 @@ static int if_spi_c2h_cmd(struct if_spi_card *card)
      BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE < LBS_CMD_BUFFER_SIZE);
      BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE < LBS_UPLD_SIZE);
 
-     /* It's just annoying if the buffer size isn't a multiple of 4, because
-      * then we might have len <  IF_SPI_CMD_BUF_SIZE but
-      * ALIGN(len, 4) > IF_SPI_CMD_BUF_SIZE */
-     BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE % 4 != 0);
+     /*
+      * It's just annoying if the buffer size isn't a multiple of
+      * DMA_ALIGN, because then we might have
+      * len < IF_SPI_CMD_BUF_SIZE but
+      * ALIGN(len, DMA_ALIGN) > IF_SPI_CMD_BUF_SIZE
+      */
+     BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE % DMA_ALIGN != 0);
 
      lbs_deb_enter(LBS_DEB_SPI);

@@ -691,7 +696,7 @@ static int if_spi_c2h_cmd(struct if_spi_card *card)
 
      /* Read the data from the WLAN module into our command buffer */
      err = spu_read(card, IF_SPI_CMD_RDWRPORT_REG,
-                             card->cmd_buffer, ALIGN(len, 4));
+                             card->cmd_buffer, ALIGN(len, DMA_ALIGN));
      if (err)
              goto out;

@@ -747,7 +752,7 @@ static int if_spi_c2h_data(struct if_spi_card *card)
      data = skb_put(skb, len);
 
      /* Read the data from the WLAN module into our skb... */
-     err = spu_read(card, IF_SPI_DATA_RDWRPORT_REG, data, ALIGN(len, 4));
+     err = spu_read(card, IF_SPI_DATA_RDWRPORT_REG, data, ALIGN(len, DMA_ALIGN));
      if (err)
              goto free_skb;

@@ -940,7 +945,7 @@ static int if_spi_host_to_card(struct lbs_private *priv,
              err = -EINVAL;
              goto out;
      }
-     blen = ALIGN(nb, 4);
+     blen = ALIGN(nb, DMA_ALIGN);
      packet = kzalloc(sizeof(struct if_spi_packet) + blen, GFP_ATOMIC);
      if (!packet) {
              err = -ENOMEM;
--

1.5.6.4

Quoted 8 lines

--
Sincerely yours,
Mike.
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Dan Williams

2009-02-03 16:39 UTC #3 lore raw

Quoted 28 lines · Andrey Yurovsky

Quoted 8 lines · Dan Williams
Quoted 6 lines · Mike Rapoport
Different SPI controllers pose different alignment requirements on DMAable buffers. It's possible to alter the SPI controller driver to use it's own properly aligned buffers for DMA and copy the data it gets from the client into these buffers. However, this approach also impacts overall performance. Adding ability to set DMA buffers alignment for SPI interface in compile time prevents unnecessary memcpy calls.
Quoted 8 lines
I'd still rather that alignment constraints were handled in the *controller* code, where the constraint actually is. If this path is followed, then every SPI-connected device for a platform would have to have specific hacks for every platform, which is quite unmaintainable. Is there a good way to fit the alignment constraints into the SPI controller code?
Dan
"struct spi_device" currently stores things like the IRQ number (ie:
"spi->irq"), how about we add an optional field to struct spi_device, something like "dma_alignment" that drivers can use as a hint? On PXA it would be set to 8, on Blackfin it can be left at 0 or set to 4 or something.
In our case we have:
- a device that needs ALIGN(4) or a multiple of 4 to work
- a controller that wants ALIGN(8)

Quoted 5 lines

So our if_spi_probe would then use the spi->dma_alignment field to choose a sane value to use with ALIGN. This would work for run-time stuff but it wouldn't help us align a static buffer correctly while Mike's approach would, though we could do something fancy to align that too. What do you think? Thanks,

That works better for me, anyone up for making the patch? Just that adding a Kconfig option really seems like the wrong approach here.

Ideally the device driver could inform the controller of it's alignment requirements, and since the controller obviously knows its own alignment requirements, the controller code would be able to choose some intersection of capabilities and handle the alignment itself. We really shouldn't be hardcoding controller constraints into the device drivers.

dan

Quoted 121 lines

-Andrey

Quoted 119 lines

Quoted 105 lines

Signed-off-by Mike Rapoport <[email protected]>

---
 drivers/net/wireless/Kconfig           |   10 ++++++++++
 drivers/net/wireless/libertas/if_spi.c |   27 ++++++++++++++++-----------
 2 files changed, 26 insertions(+), 11 deletions(-)

drivers/net/wireless/Kconfig +10 -0

index fe819a7..3bbb7b2 100644
@@ -157,6 +157,16 @@ config LIBERTAS_SPI
      ---help---
        A driver for Marvell Libertas 8686 SPI devices.
 
+config LIBERTAS_SPI_DMA_ALIGN
+     int "DMA buffers alignment for SPI interface"
+     depends on LIBERTAS_SPI
+     default 4 if !ARCH_PXA
+     default 8 if ARCH_PXA
+     ---help---
+       Different SPI controllers pose different alignment
+       requirements on DMAable buffers. Allow proper setting of
+       this value in compile-time.
+
 config LIBERTAS_DEBUG
      bool "Enable full debugging output in the Libertas module."
      depends on LIBERTAS

drivers/net/wireless/libertas/if_spi.c +16 ~~-12~~

index 07311e7..3499948 100644
@@ -33,10 +33,12 @@
 #include "dev.h"
 #include "if_spi.h"
 
+#define DMA_ALIGN CONFIG_LIBERTAS_SPI_DMA_ALIGN
+
 struct if_spi_packet {
-     struct list_head                list;
-     u16                             blen;
-     u8                              buffer[0] __attribute__((aligned(4)));
+     struct list_head        list;
+     u16                     blen;
+     u8                      buffer[0] __attribute__((aligned(DMA_ALIGN)));
 };
 
 struct if_spi_card {

@@ -73,7 +75,7 @@ struct if_spi_card {
      struct semaphore                spi_ready;
      struct semaphore                spi_thread_terminated;
 
-     u8                              cmd_buffer[IF_SPI_CMD_BUF_SIZE];
+     u8                              cmd_buffer[IF_SPI_CMD_BUF_SIZE] __attribute__((aligned(DMA_ALIGN)));
 
      /* A buffer of incoming packets from libertas core.
       * Since we can't sleep in hw_host_to_card, we have to buffer

@@ -665,10 +667,13 @@ static int if_spi_c2h_cmd(struct if_spi_card *card)
      BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE < LBS_CMD_BUFFER_SIZE);
      BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE < LBS_UPLD_SIZE);
 
-     /* It's just annoying if the buffer size isn't a multiple of 4, because
-      * then we might have len <  IF_SPI_CMD_BUF_SIZE but
-      * ALIGN(len, 4) > IF_SPI_CMD_BUF_SIZE */
-     BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE % 4 != 0);
+     /*
+      * It's just annoying if the buffer size isn't a multiple of
+      * DMA_ALIGN, because then we might have
+      * len < IF_SPI_CMD_BUF_SIZE but
+      * ALIGN(len, DMA_ALIGN) > IF_SPI_CMD_BUF_SIZE
+      */
+     BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE % DMA_ALIGN != 0);
 
      lbs_deb_enter(LBS_DEB_SPI);

@@ -691,7 +696,7 @@ static int if_spi_c2h_cmd(struct if_spi_card *card)
 
      /* Read the data from the WLAN module into our command buffer */
      err = spu_read(card, IF_SPI_CMD_RDWRPORT_REG,
-                             card->cmd_buffer, ALIGN(len, 4));
+                             card->cmd_buffer, ALIGN(len, DMA_ALIGN));
      if (err)
              goto out;

@@ -747,7 +752,7 @@ static int if_spi_c2h_data(struct if_spi_card *card)
      data = skb_put(skb, len);
 
      /* Read the data from the WLAN module into our skb... */
-     err = spu_read(card, IF_SPI_DATA_RDWRPORT_REG, data, ALIGN(len, 4));
+     err = spu_read(card, IF_SPI_DATA_RDWRPORT_REG, data, ALIGN(len, DMA_ALIGN));
      if (err)
              goto free_skb;

@@ -940,7 +945,7 @@ static int if_spi_host_to_card(struct lbs_private *priv,
              err = -EINVAL;
              goto out;
      }
-     blen = ALIGN(nb, 4);
+     blen = ALIGN(nb, DMA_ALIGN);
      packet = kzalloc(sizeof(struct if_spi_packet) + blen, GFP_ATOMIC);
      if (!packet) {
              err = -ENOMEM;
--

1.5.6.4

Quoted 8 lines

--
Sincerely yours,
Mike.
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Mike Rapoport

author

2009-02-04 14:51 UTC #4 lore raw

Quoted 9 lines · Dan Williams

Quoted 8 lines · Andrey Yurovsky
Quoted 7 lines · Dan Williams
Quoted 6 lines · Mike Rapoport
Different SPI controllers pose different alignment requirements on DMAable buffers. It's possible to alter the SPI controller driver to use it's own properly aligned buffers for DMA and copy the data it gets from the client into these buffers. However, this approach also impacts overall performance. Adding ability to set DMA buffers alignment for SPI interface in compile time prevents unnecessary memcpy calls.

Quoted 6 lines

Quoted 6 lines
Quoted 6 lines
I'd still rather that alignment constraints were handled in the *controller* code, where the constraint actually is. If this path is followed, then every SPI-connected device for a platform would have to have specific hacks for every platform, which is quite unmaintainable. Is there a good way to fit the alignment constraints into the SPI controller code?

I completely agree that a driver should not have platform specific hacks because of controller limitation. However, adding Kconfig option provides working, although far from perfect solution.
I agree that SPI controller and probably the entire SPI subsystem code should be reworked to allow proper DMAing of different devices with different controllers. But until it is done being able to use G-SPI 8686 on PXA seems to me worth adding some ugly bits to libertas Kconfig. If you disagree with it I can keep this patch on top of my private tree until SPI is reworked, or 8686 gets EOL.

Quoted 6 lines

Quoted 6 lines
Quoted 1 line
Dan
"struct spi_device" currently stores things like the IRQ number (ie:
"spi->irq"), how about we add an optional field to struct spi_device, something like "dma_alignment" that drivers can use as a hint? On PXA it would be set to 8, on Blackfin it can be left at 0 or set to 4 or something.

Maybe we can have it as a libertas_spi_platform_data field? Anyway, the platform code should be aware of controller-specific quirks.

Quoted 4 lines

Quoted 4 lines
In our case we have:
- a device that needs ALIGN(4) or a multiple of 4 to work
- a controller that wants ALIGN(8)

Quoted 8 lines

Quoted 5 lines
So our if_spi_probe would then use the spi->dma_alignment field to choose a sane value to use with ALIGN. This would work for run-time stuff but it wouldn't help us align a static buffer correctly while Mike's approach would, though we could do something fancy to align that too. What do you think? Thanks,
That works better for me, anyone up for making the patch? Just that adding a Kconfig option really seems like the wrong approach here.

I've added the 'dma_alignment' field to spi_device and tried to use its value with ALIGN without modifying static buffer alignment.

I've tested a large file transfer with three different options: if_spi.c without any alignment changes, my patch with Kconfig option applied, and dynamic parameter to ALIGN. The numbers I get are 200-210 Kb/sec, 480-490 Kb/sec and 290-300 Kb/sec respectively.

I'll try to see how is it possible to properly align the static buffer. Any ideas are welcome.

Quoted 129 lines

dan

Quoted 120 lines

-Andrey

Quoted 118 lines

Quoted 105 lines

Signed-off-by Mike Rapoport <[email protected]>

---
 drivers/net/wireless/Kconfig           |   10 ++++++++++
 drivers/net/wireless/libertas/if_spi.c |   27 ++++++++++++++++-----------
 2 files changed, 26 insertions(+), 11 deletions(-)

drivers/net/wireless/Kconfig +10 -0

index fe819a7..3bbb7b2 100644
@@ -157,6 +157,16 @@ config LIBERTAS_SPI
      ---help---
        A driver for Marvell Libertas 8686 SPI devices.
 
+config LIBERTAS_SPI_DMA_ALIGN
+     int "DMA buffers alignment for SPI interface"
+     depends on LIBERTAS_SPI
+     default 4 if !ARCH_PXA
+     default 8 if ARCH_PXA
+     ---help---
+       Different SPI controllers pose different alignment
+       requirements on DMAable buffers. Allow proper setting of
+       this value in compile-time.
+
 config LIBERTAS_DEBUG
      bool "Enable full debugging output in the Libertas module."
      depends on LIBERTAS

drivers/net/wireless/libertas/if_spi.c +16 ~~-12~~

index 07311e7..3499948 100644
@@ -33,10 +33,12 @@
 #include "dev.h"
 #include "if_spi.h"
 
+#define DMA_ALIGN CONFIG_LIBERTAS_SPI_DMA_ALIGN
+
 struct if_spi_packet {
-     struct list_head                list;
-     u16                             blen;
-     u8                              buffer[0] __attribute__((aligned(4)));
+     struct list_head        list;
+     u16                     blen;
+     u8                      buffer[0] __attribute__((aligned(DMA_ALIGN)));
 };
 
 struct if_spi_card {

@@ -73,7 +75,7 @@ struct if_spi_card {
      struct semaphore                spi_ready;
      struct semaphore                spi_thread_terminated;
 
-     u8                              cmd_buffer[IF_SPI_CMD_BUF_SIZE];
+     u8                              cmd_buffer[IF_SPI_CMD_BUF_SIZE] __attribute__((aligned(DMA_ALIGN)));
 
      /* A buffer of incoming packets from libertas core.
       * Since we can't sleep in hw_host_to_card, we have to buffer

@@ -665,10 +667,13 @@ static int if_spi_c2h_cmd(struct if_spi_card *card)
      BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE < LBS_CMD_BUFFER_SIZE);
      BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE < LBS_UPLD_SIZE);
 
-     /* It's just annoying if the buffer size isn't a multiple of 4, because
-      * then we might have len <  IF_SPI_CMD_BUF_SIZE but
-      * ALIGN(len, 4) > IF_SPI_CMD_BUF_SIZE */
-     BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE % 4 != 0);
+     /*
+      * It's just annoying if the buffer size isn't a multiple of
+      * DMA_ALIGN, because then we might have
+      * len < IF_SPI_CMD_BUF_SIZE but
+      * ALIGN(len, DMA_ALIGN) > IF_SPI_CMD_BUF_SIZE
+      */
+     BUILD_BUG_ON(IF_SPI_CMD_BUF_SIZE % DMA_ALIGN != 0);
 
      lbs_deb_enter(LBS_DEB_SPI);

@@ -691,7 +696,7 @@ static int if_spi_c2h_cmd(struct if_spi_card *card)
 
      /* Read the data from the WLAN module into our command buffer */
      err = spu_read(card, IF_SPI_CMD_RDWRPORT_REG,
-                             card->cmd_buffer, ALIGN(len, 4));
+                             card->cmd_buffer, ALIGN(len, DMA_ALIGN));
      if (err)
              goto out;

@@ -747,7 +752,7 @@ static int if_spi_c2h_data(struct if_spi_card *card)
      data = skb_put(skb, len);
 
      /* Read the data from the WLAN module into our skb... */
-     err = spu_read(card, IF_SPI_DATA_RDWRPORT_REG, data, ALIGN(len, 4));
+     err = spu_read(card, IF_SPI_DATA_RDWRPORT_REG, data, ALIGN(len, DMA_ALIGN));
      if (err)
              goto free_skb;

@@ -940,7 +945,7 @@ static int if_spi_host_to_card(struct lbs_private *priv,
              err = -EINVAL;
              goto out;
      }
-     blen = ALIGN(nb, 4);
+     blen = ALIGN(nb, DMA_ALIGN);
      packet = kzalloc(sizeof(struct if_spi_packet) + blen, GFP_ATOMIC);
      if (!packet) {
              err = -ENOMEM;
--

1.5.6.4

Quoted 8 lines

--
Sincerely yours,
Mike.
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Signature · 2 lines

Sincerely yours,
Mike.